Enhancement of the Effectiveness of Lyt-2+ T-Cells for Adoptive Chemoimmuno- therapy by Short-Term Exposure of Tumor-bearer Spleen Cells to Polyethylene Glycol and/or MelphaIan1

Uncultured tumor-infiltrated spleen cells (TISpC) from mice bearing large (20-22 mm) s.c. MOPC-315 plasmacytomas were previously shown to be ineffective in bringing about the cure of mice bearing a nonpalpable (Day 4) tumor that had been treated with a subcurative dose (10 mg/kg) of cyclophosphamide (i.e.. adoptive chemoimmunotherapy, U M) (M. B. Mokyr, J. C. D. Hengst, and S. Dray, Cancer Res., 42: 974-979, 1982). Here we show that TISpC cultured for 5 days in the presence of inactivated MOPC-315 stimulator cells acquire some effectiveness in curing mice by ACIT, and this effectiveness is greatly enhanced if polyethylene glycol 6000 (PEG) is also added to the culture. The Lyt 2' T-cells, and not the L3T4+ T-cells, are responsible for the effectiveness of the cultured TISpC in ACIT. In fact, the L3T4* T-cells are apparently not required even during culture of TISpC for the generation of Lyt 2* T-cells effective in ACIT. Although the TISpC cultured with MOPC315 cells and PEG contained approximately twice as many Lyt 2* cells as did TISpC cultured without PEG, the increase in the activity of the former cells is not due simply to the increase in the percentage of Lyt 2* cells, but is most likely due to an increase in the percentage and/or activity of Lyt 2* cells with specificity for MOPC-315-associated anti gens. The effectiveness of TISpC cultured with MOPC-315 stimulator cells and PEG in ACIT can be enhanced even further by pretreatmentof these cells with the immunomodulatingagent melphalan (0.5 nmol/ml) prior to culture initiation. Thus, the above methods of culture render ineffective lymphoid cells effective in ACIT andare suitable for evaluation in protocols for human cancer therapy.